PHYSICS/BK21 SEMINAR [4.26]

[ Flexible terahertz metamaterials exhibiting broadband extremely high index of refraction ]

* Speaker : Prof. Bumki Min [Department of Mechanical Engineering, KAIST]

  * Place  : Physics Seminar Room (Science Bldg, 3-103)

   * Date & Time : Apr, 26 (Mon)  2:00 ~ 3:00 pm

Abstract

Controlling electromagnetic properties of materials, beyond the limit that was unattainable by naturally existing substances, becomes a reality with the advent of the conceptual breakthrough called ‘metamaterials’.  The collection of artificially-structured ‘atoms’ promises a vast variety of unexpected physical phenomena such as negative refractive index, invisibility cloak, and imaging beyond the diffraction limit.  However, from the perspective of manipulating refractive index, experimental realization of negative refractive index has been the main focus thus far.  In this talk, it is shown that broadband high index of refraction can be realized with large-area, free-standing, terahertz metamaterials composed of strongly-coupled unit cells.  By increasing the effective permittivity and decreasing diamagnetic response of the unit cell with small metallic volume, a peak refractive index of 35 alongside a quasi-static limiting value of 12 are experimentally realized at the terahertz frequency regime.  As a natural extension of the single layer metamaterials, quasi-three-dimensional high-refractive-index metamaterials are fabricated with successive stacking of planar metamaterial layers.  In stark contrast to the single-layer metamaterials and multilayer metamaterials with small interlayer spacing, the progressive formation of a bandgap and the emergence of Bloch eigenmodes are observed below the bandgap as the number of meta-layers is increased for multi-layered metamaterials with large interlayer spacing, indicative of the transition from metamaterial regime to photonic-crystal regime.  These metamaterials with high refractive indices will open up a new possibility in the development of ultra-compact subwavelength-scale terahertz functional devices.

Contact Person : Gunsu S. Yun, Research Prof. of Physics  (054-279-5831, gunsu@postech.ac.kr )